Radio communication devices, such as pagers, typically receive and decode radio frequency (RF) signals to recover information contained therein. In many conventional radio communication devices, a received signal is first converted from the radio frequency at which it is received to baseband, subsequent to which data is recovered from the signal. The data is then processed by decoding circuitry, such as a microcomputer, which decodes the included information.
In order to recover the data from an incoming signal, tracking circuitry tracks the data to determine signal highs and lows, i.e., signal peaks and valleys. Once the incoming signal has stabilized and the highs and lows of the signal have been acquired, the highs and lows are utilized to generate from the incoming signal the stream of data.
In some conventional radio communication devices, the decay rate at which the signal can be tracked is determined by a capacitor included in analog tracking circuitry. Typically, the value of the capacitor is set such that the decay rate is relatively slow. The slow decay rate provides for the more accurate tracking of the signal because small signal deviations will not affect the highs and lows. However, the slow decay rate can sometimes cause problems. By way of example, when a noise spike occurs on the signal, the tracking circuitry follows the noise spike. Thereafter, a portion of the desired signal may be missed during the slow decay from the higher noise voltage to the lower signal voltage.
Other conventional radio communication devices digitally track an incoming signal at the direction of a controller, such as a microcomputer. Typically, this type of tracking circuitry holds the values of the most recent highs and lows of the signal, rather than automatically decaying like the above-described analog tracking circuitry, until directed by the microcomputer to decay, i.e., decrement counters to track a converging signal. In this manner, the digital tracking circuitry holds signal highs and lows, thereby preventing small signal deviations from affecting the highs and lows and thus the generated data. However, the microcomputer subroutines for directing the tracking circuitry generally consume space in the receiver memory that is already at a premium. Additionally, time is wasted in which the microcomputer must retrieve information from memory, process the information, and issue the appropriate instructions to the tracking circuitry.
Thus, what is needed is an improved method for tracking an incoming signal to acquire signal highs and lows that prevents situations in which portions of a desired signal are missed. The method should also prevent small deviations in the signal from affecting the signal highs and lows. Furthermore, implementation of the method should not require additional space in memory for storage of microcomputer subroutines or additional processing time in which the microcomputer generates commands to direct the tracking circuitry.